A Machine-To-Machine (M2M) technology is a networked application and service that use a machine as a terminal and use intelligent interaction as a core. In the M2M technology, cooperative work between machines is implemented by using data transmission between the machines, which greatly improves productivity. With development of mobile communications technologies, M2M services represented by intelligent metering, vehicle condition monitoring, Internet of Vehicles, industrial monitoring, and the like gradually become popular application services.
Main characteristics of the M2M technology are as follows: numerous terminals; a small data packet service is used for communication between different terminals; and a discontinuous transmission manner is used for communication between different terminals, which has a low latency requirement. Therefore, a Universal Mobile Telecommunications System (UMTS) becomes a communications system generally used to implement the M2M technology. When different terminals communicate with each other, the UMTS is used for sending. In the UMTS, the small data packet service may work in a CELL_FACH mode of a Forward Access Channel (FACH) or in an enhanced CELL_FACH Radio Resource Control (RRC) connected mode, and a terminal may transmit data on a Random Access Channel (RACH). That is, when the terminal needs to transmit data, the terminal first applies for and uses an access resource of a network; after obtaining the access resource by means of applying, the terminal sends the data by using the access resource; after transmitting the data, the terminal releases the access resource. Therefore, the access resource of the UMTS can be efficiently used.
Because data is transmitted on a RACH, a terminal usually requests, in a manner of sending a preamble sequence, to use an access resource. Specifically, when the terminal needs to transmit data, the terminal first sends a preamble sequence at an access slot (AS) boundary. A base station detects preamble sequences, and when the preamble sequence sent by the terminal is detected and there is an available access resource, the base station sends an acquisition indicator (AI) to the terminal. If the terminal receives the AI within a preset time after sending the preamble sequence, the terminal sends the data within a particular time after receiving the AI. If the terminal receives no AI within a preset time after sending the preamble sequence, the terminal re-sends a preamble sequence at a next AS boundary and requests again to use an access resource.
However, if there are limited available RACH access resources and numerous M2M terminals, multiple terminals may simultaneously request to use an access resource. For example, in a vehicle condition monitoring system, at a particular moment, many vehicle-mounted terminals may simultaneously report vehicle condition data to a server. In this case, a base station may simultaneously receive preamble sequences sent by many terminals, which causes overload of the base station. Further, because a limited quantity of terminals are allowed to access a network at a same moment, many terminals cannot receive an AI within a preset time after sending preamble sequences; and many terminals that receive no AI may re-send preamble sequences to request again to use an access resource, which further aggravates the load of the base station.